1. Field of the invention
The present invention relates to a mounting structure for a sewing machine motor built into a machine frame of a sewing machine.
2. Description of Related Art
U.S. Pat. No. 3,832,613 and Japanese Patent Publication No. 1-21996 disclose a sewing machine wherein a main shaft is rotatably supported in a machine frame and a motor for driving the sewing machine is mounted in the machine frame in an opposed relationship to an end of the main shaft. In such a sewing machine, the motor shaft of the motor is connected to the main shaft by means of a coupling.
However, in such a sewing machine it is necessary to have concentricity and straightness between the main shaft and the motor shaft. If the concentricity and the straightness are insufficient, there is a possibility that a stress will be applied to the bearings for the main shaft and the motor shaft or the coupling between both the shafts, causing breakage of the bearings or the coupling, seizure of the main shaft and the motor shaft, or increase in load torque.
Accordingly, it is necessary to increase the mounting accuracy of the main shaft with respect to the machine frame, the mounting accuracy of the motor with respect to the machine frame, and the mounting accuracy of the motor shaft with respect to the housing of the motor. To attain these increased mounting accuracies, highly sophisticated manufacturing techniques are required which, in turn, cause an increase in manufacturing costs.